Caracterização das estratégias ecofisiológicas de samambaias em resposta à inundação na restinga de Maricá, Rio de Janeiro, Brasil

As matas inundáveis e brejos presentes nas restingas desencadeiam uma série de processos que influenciam as características físico-químicas e biológicas do solo, levando as plantas a apresentarem mecanismos de aclimatação ou adaptação ao estresse da inundação, como alterações morfológicas e fisiológicas de forma a minimizar os efeitos da falta de oxigênio. Dentre as espécies vegetais de samambaias ocorrentes em ambientes inundáveis nas restingas, se destacam três espécies: Acrostichum danaeifolium Langsd. & Fisch., Blechnum serrulatum Rich. e Thelypteris interrupta (Willd.) K.Iwats. O objetivo deste trabalho é caracterizar os aspectos ecofisiológicos que os esporófitos dessas samambaias apresentam para sobreviver em ambientes de inundação na restinga de Maricá, estado do Rio de Janeiro. Neste sentido, foi determinada a caracterização física e química dos sítios de ocorrências destas samambaias, as variações foliares entre elas, espessura, densidade, massa por unidade de folha, teor de clorofilas e atributos quantitativos das células epidérmicas, além da quantificação e determinação à distribuição dos carboidratos. Para as variáveis dos vegetais foram feitas coletas na estação chuvosa e seca e para variáveis do solo na estação seca. Os sítios analisados se mostraram extremamente ácidos, de baixa fertilidade e com toxidez por macro e micro nutrientes, indicando que as samambaias apresentam tolerância a estes fatores. Na época chuvosa (inundação), as samambaias apresentaram queda na densidade foliar, acompanhada de um aumento de massa por unidade de folha. Esta habilidade de conseguir ganhar massa seca por área classifica todas as samambaias analisadas como tolerantes à inundação. Os altos valores de carboidratos solúveis nas folhas indicam aumento da degradação do amido foliar e o menor teor de carboidrato solúvel encontrado nos caules explicita a redução na respiração das raízes destas plantas sob anoxia/ hipoxia, para evitar a oxidação e o incremento do estoque de amido de reserva, elucidando estratégia de tolerância à inundação. A menor disponibilidade de água na estação seca afeta diretamente os atributos foliares diminuindo o índice estomático, a suculência e a massa por unidade de folha, no qual reflete na queda das concentrações de clorofilas. Os menores valores nas concentrações de clorofila têm influencia direta na presença de amidos foliar que são estocado e, alterando toda a dinâmica dos carboidratos nestas espécies. A análise do sítio onde cresce Acrostichum danaeifolium indica níveis críticos de Na no solo e provavelmente, a produção de mucilagem no caule e no pecíolo é uma estratégia de tolerância ao ambiente salino e inundado. O elevado índice de cobertura de Blechnum serrulatum em ambientes inundados indica que esta espécie possui adaptações a solos hidromórficos, entre elas, grande capacidade de estocagem de amido no caule. A maior sinuosidade das células epidérmicas em T. interrupta permite uma alta suculência mantendo o status hidrológico da folha em ambas as estações. Os resultados apresentados, além de agregar informações sobre a biologia das samambaias nos neotrópicos, irão contribuir para a compreensão da dinâmica de ocupação de espécies herbáceas em ambientes alagáveis nas restingas brasileiras

The effect of sublethal concentration of DimilinR (TH6040) on the larval development of the mud-crab Rhithropanopeus harrisii (Gould)

Sublethal DimilinR (insecticide) concentration significantly decreased the percentage survival of larval R. harrisii . This decrease was marked at low salinities, when it may have become toxic. This was true for both 25 and 30 C. Duration of larval development did not seem to be affected by sublethal DimilinR concentrations even in extremely low or high salinities. High temperature, however, shortened the time of development. No anatomical abnormality was observed. These findings are only tentative as more replicates of the experiments are needed before definite conclusions can be reached. It will be desirable to work with more salinity-temperature combinations to get a complete picture of sublethal effects under different environmental conditions.

Novel equation to determine the hepatic triglyceride concentration in humans by MRI: diagnosis and monitoring of NAFLD in obese patients before and after bariatric surgery

Background: Non-alcoholic fatty liver disease (NAFLD) is caused by abnormal accumulation of lipids within liver cells. Its prevalence is increasing in developed countries in association with obesity, and it represents a risk factor for non-alcoholic steatohepatitis (NASH), cirrhosis and hepatocellular carcinoma. Since NAFLD is usually asymptomatic at diagnosis, new non-invasive approaches are needed to determine the hepatic lipid content in terms of diagnosis, treatment and control of disease progression. Here, we investigated the potential of magnetic resonance imaging (MRI) to quantitate and monitor the hepatic triglyceride concentration in humans. Methods: A prospective study of diagnostic accuracy was conducted among 129 consecutive adult patients (97 obesity and 32 non-obese) to compare multi-echo MRI fat fraction, grade of steatosis estimated by histopathology, and biochemical measurement of hepatic triglyceride concentration (that is, Folch value). Results: MRI fat fraction positively correlates with the grade of steatosis estimated on a 0 to 3 scale by histopathology. However, this correlation value was stronger when MRI fat fraction was linked to the Folch value, resulting in a novel equation to predict the hepatic triglyceride concentration (mg of triglycerides/g of liver tissue = 5.082 + (432.104 * multi-echo MRI fat fraction)). Validation of this formula in 31 additional patients (24 obese and 7 controls) resulted in robust correlation between the measured and estimated Folch values. Multivariate analysis showed that none of the variables investigated improves the Folch prediction capacity of the equation. Obese patients show increased steatosis compared to controls using MRI fat fraction and Folch value. Bariatric surgery improved MRI fat fraction values and the Folch value estimated in obese patients one year after surgery. Conclusions: Multi-echo MRI is an accurate approach to determine the hepatic lipid concentration by using our novel equation, representing an economic non-invasive method to diagnose and monitor steatosis in humans.

Spectroscopic properties of fluorophosphate glass with high Er(3+)supercript stop concentration

Fluorophosphate glass with 4 mol.% ErF3 content was prepared. The different scanning calorimetry was conducted. Raman spectrum, infrared transmission spectrum, absorption spectrum were measured. Fluorescence spectrum and lifetime of emission around 1.53 mu m were measured under 970 nm laser diode excitation. The metaphosphate content in the composition is limited, but the maximum phonon energy of glass amounts to 1290 cm- 1, and is comparatively high. The full width at half maximum is about 56 nm, and is wider than for most of the materials investigated. The measured lifetime of I-4(13/2) -> I-4(15/2) transition, contributed by the high phonon energy, inefficient interaction of Er3+ ions, and low water content, amounts to no less than 7.36 ms though the Er3+ concentration is high. This work might provide useful information for the development of compact optical devices.

Concentration quenching in erbium-doped tellurite glasses

Er2O3-doped TeO2-ZnO-La2O3 modified tellurite glasses were prepared by the conventional melt-quenching method, and the Er3+ : I-4(13/2) -> I-4(15/2) fluorescence properties have been studied for different Er3+ concentrations. Infrared spectra were measured in order to estimate the exact content of OH- groups in samples. Based on the electric dipole-dipole interaction theory, the interaction parameter, C-Er,(Er), for the migration rate of Er3+ : I-4(13/2) -> I-4(13/2) in modified tellurite glass was calculated. Finally, the concentration quenching mechanism using a model based on energy transfer and quenching by hydroxyl (OH-) groups was presented. (c) 2005 Elsevier B.V. All rights reserved.

Effects of Yb ion concentration on the spectral properties of lead silica glasses

The spectral properties in different concentration of Yb ions (0.5-5 mol%)-doped silica glasses are explored in this paper. The glasses are prepared by traditional melting method. The absorption spectra and the fluorescent lifetime (tau(f)) are measured at room temperature and low temperature (18 K). The stimulated cross-section (sigma(emi)) and potential laser properties (beta(min), I-sat, I-min) are calculated based on the absorption spectra. The absorption cross-section (sigma(abs)) are in the range 1.08 x 10(-20) - 1.18 x 10(-20) cm(2) in different glasses, the fluorescence lifetime (tau(f)) change from 1.9 to 1.2 ms with the increase of Yb3+ concentration. The potential laser properties indicate that lead silica glass is a good host for highly Yb ion doping glass. (c) 2005 Elsevier B.V. All rights reserved.

High Er3+ concentration low refractive index fluorophosphate glass for evanescent wave optical amplifiers

This is about the first reported laser glass with very low no, high Er3+ concentration and no quenching. In this work, a series of high Er3+ concentration (10.6-12.2 x 10(20) ions/cm(3)), low refractive index (n(1550) < 1.47) and relatively high fluorescence lifetime (6.8-12.6 ms) fluorophosphate glasses were made. A cw-pumping evanescent wave optical amplifier experiment was performed with it, and a relative gain of around 2dB at 1550 nm wavelength was achieved while the noise level was almost unchanged. To our knowledge, this is the first successful relative gain in evanescent wave optical amplifiers (EWOA) demonstrated with cw pumping. It is a valuable study of specially designed fluorophosphate glass suitable for EWOA communication experiment. (C) 2008 Elsevier B.V. All rights reserved.